Ritonavir inhibits HIF-1α-mediated VEGF expression in retinal pigment epithelial cells in vitro

Retinopathy Associated With Ritonavir Treatment for HIV Infection: A Case Series Reappraisal in the COVID-19 Era

Purpose: To report 3 cases of retinopathy secondary to ritonavir use in the treatment of HIV. Methods: A retrospective review of patient records was performed for data including ophthalmic examination findings, demographic and HIV clinical characteristics, and progression of maculopathy disease. The review identified 3 patients with a history of HIV treated with antiretroviral therapy including ritonavir who had been evaluated for bilateral vision loss in both eyes. Results: A fundus examination of each patient revealed characteristic macular atrophy, and optical coherence tomography demonstrated corresponding central outer retinal atrophy. Uveitis workup results were unremarkable. Given the characteristics of macular atrophy, history of ritonavir use, and the absence of intraocular inflammation, all 3 patients were diagnosed with bilateral ritonavir-associated retinopathy. Each patients' vision continued to deteriorate, even after the cessation of ritonavir. Conclusions: Ritonavir toxicity should be considered in the differential diagnosis of retinopathy among patients with an exposure history.

Honokiol Attenuates Choroidal Neovascularization by Inhibiting the Hypoxia-Inducible Factor-α/Vascular Endothelial Growth Factor Axis via Nuclear Transcription Factor-Kappa B Activation

PURPOSE

Honokiol is a lignan isolated from Magnolia officinalis and exhibits anti-angiogenic properties. This study was conducted to investigate the role of honokiol in choroidal neovascularization.

METHODS

C57BL/6 mice were treated with honokiol at 10-20 mg/kg by daily intraperitoneal injection from day 1 to 6 after laser photocoagulation. ARPE-19 cells were cultured under hypoxic conditions with or without the presence of honokiol. After laser photocoagulation and honokiol treatment, hematoxylin and eosin staining, immunofluorescence and fundus fluorescein angiography were used to analyze the effect of honokiol on choroidal neovascularization formation. Quantitative real-time PCR, western blot, enzyme-linked immunosorbent assay, immunofluorescence, luciferase assay, and chromatin immunoprecipitation were performed to explore the mechanism of honokiol in the pathological process of choroidal neovascularization. Finally, the role of honokiol on the human choroidal vascular endothelial cells was detected by using 5-ethynyl-20-deoxyuridine assay, Transwell and Tube formation assays.

RESULTS

The results of hematoxylin and eosin staining and immunofluorescence suggested that honokiol reduced the thickness, length, and area of choroidal neovascularization lesions in laser-induced choroidal neovascularization mouse model. Fundus fluorescein angiography showed that choroidal neovascularization leakage was reduced in honokiol group and the concentration of 20 mg/kg showed better effects. Mechanism studies have shown that honokiol exerted inhibitory effects on choroidal neovascularization by inactivating hypoxia-inducible factor-1α/vascular endothelial growth factor axis through the nuclear transcription factor-kappa B signaling pathway. The same results were obtained in ARPE-19 cells under hypoxic conditions. Furthermore, the conditional medium of retinal pigmented epithelial cells promoted the proliferation, migration, and tube formation of human choroidal vascular endothelial cells, while honokiol reversed these.

CONCLUSION

We demonstrated that honokiol attenuated choroidal neovascularization formation by inactivating the hypoxia-inducible factor-1α/vascular endothelial growth factor axis through nuclear transcription factor-kappa B signaling pathway.

Epigallocatechin-3-Gallate, an Active Green Tea Component to Support Anti-VEGFA Therapy in Wet Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a largely incurable disease and an emerging problem in aging societies. It occurs in two forms, dry and wet (exudative, neovascular), which may cause legal blindness and sight loss. Currently, there is not any effective treatment for dry AMD. Meanwhile, repeated intravitreal injections with antibodies effective against vascular endothelial growth factor A (VEGFA) slow down wet AMD progression but are not free from complications. (-)-Epigallocatechin-3-gallate (EGCG) is an active compound of green tea, which exerts many beneficial effects in the retinal pigment epithelium and the neural retina. It has been reported to downregulate the VEGFA gene by suppressing its activators. The inhibition of mitogen-activated protein kinases 1 and 3 (MAPK1 and MAPK3) may lie behind the antiangiogenic action of EGCG mediated by VEGFA. EGCG exerts protective effects against UV-induced damage to retinal cells and improves dysfunctional autophagy. EGCG may also interact with the mechanistic target rapamycin (MTOR) and unc-51-like autophagy activating kinase (ULK1) to modulate the interplay between autophagy and apoptosis. Several other studies report beneficial effects of EGCG on the retina that may be related to wet AMD. Therefore, controlled clinical trials are needed to verify whether diet supplementation with EGCG or green tea consumption may improve the results of anti-VEGFA therapy in wet AMD.

Combination of pigment epithelium derived factor with anti-vascular endothelial growth factor therapy protects the neuroretina from ischemic damage

Ocular ischemia is a vision-threatening disease, and is a medical condition associated with many ocular diseases. Anti-VEGF therapy has limitations related to its side effects and suppression of physiological revascularization. Pigment epithelium derived factor (PEDF) has anti-angiogenesis and neurotrophic neuroprotective functions and is a promising agent in the treatment of ischemia-induced retinal neurodegeneration. The purpose of this study is to investigate the effect of PEDF and anti-VEGF and the combined therapy on the ischemic rat eye model ex vivo. In this study, the PEDF protein, anti-VEGF drug (Avastin) or the combination of PEDF and Avastin were intravitreally injected immediately after eye enucleation. Then the eyes were incubated in Dulbecco's modified eagle medium (DMEM) at 4 ℃ for 14 h. After that the eyes were fixed immediately by formalin. VEGF, PEDF and glial fibrillary acidic protein (GFAP) were detected by immunohistochemical (IHC) staining. The IHC staining intensity was evaluated for each eye. Compared to the groups treated by vehicle, PEDF, and anti-VEGF alone, the value of staining intensity of VEGF and GFAP was significantly reduced in the retina and choroidal vessels of the PEDF/Anti-VEGF treatment group. The intravitreally injected PEDF protein can locate in the retina and the choroidal vessels. Compared to the vehicle-treatment group, both the PEDF-treatment and the PEDF/Anti-VEGF treatment groups showed significantly decreased number of TUNEL-positive nuclei, and the PEDF/Anti-VEGF treatment group had the least TUNEL-positive nuclei. Combination of PEDF and an anti-VEGF drug (Avastin) is a possible therapeutic strategy against ischemic retinal and choroidal diseases.

Uncontrolled Oxygen Levels in Cultures of Retinal Pigment Epithelium: Have We Missed the Obvious?

Retinal pigment epithelium (RPE) is the outermost layer of retina located between the photoreceptor cells and the choroid. This highly-polarized monolayer provides critical support for the functioning of the other parts of the retina, especially photoreceptors. Methods of culturing RPE have been under development since its establishment in 1920s. Despite considering various factors, oxygen (O₂) levels in RPE microenvironments during culture preparation and experimental procedure have been overlooked. O₂ is a crucial parameter in the cultures, and therefore, maintaining RPE cells at O₂ levels different from their native environment (70-90 mm Hg of O₂) could have unintended consequences. Owing to the importance of the topic, lack of sufficient discussion in the literature and to encourage future research, this paper will focus on uncontrolled O₂ level in cultures of RPE cells.

Assessing the protective effects of cryptotanshinone on CoCl2‑induced hypoxia in RPE cells

The development of several retinal diseases is closely related to hypoxia. As a component of the Traditional Chinese medicine Salvia miltiorrhiza, the effects of cryptotanshinone (CT) on retinal cells under hypoxic conditions are not well understood. The aim of the present study was to explore how CT exerted its protective effects on retinal pigment epithelium (RPE) cells under hypoxic conditions induced by cobalt chloride (CoCl₂). The effects of CT were investigated using a Cell Counting Kit-8 assay, Annexin V-FITC/PI staining, reverse transcription-quantitative PCR and western blotting in ARPE-19 cells. CT (10 and 20 µM) reduced the CoCl₂-induced increase in vascular endothelial growth factor expression and hypoxia-inducible transcription factor-1α expression in ARPE-19 cells. Additionally, CT alleviated hypoxia-induced apoptosis by regulating Bcl-2 and Bax protein expression. CT treatment also reduced the increase in the mRNA levels of IL-6, IL-1β and TNF-α induced by CoCl₂. In summary, CT may protect RPE cells against apoptosis and inflammation in CoCl₂-induced hypoxia, and these results warrant further in vivo study into its value as a drug for treating hypoxic eye diseases.

Case Report: Multimodal Imaging of Toxic Retinopathies Related to Human Immunodeficiency Virus Antiretroviral Therapies: Maculopathy vs. Peripheral Retinopathy. Report of Two Cases and Review of the Literature

Purpose: We report two patients with toxic retinopathy from either ritonavir or didanosine and reviewed the literature on the topics. We provide an overview of the retinal toxicity of these two antiretroviral drugs in human immunodeficiency virus-positive patients.

Methods: First, we performed a retrospective study of the medical charts of two patients examined by us, one with ritonavir maculopathy and one with didanosine peripheral retinopathy. Secondly, we searched the world literature for similar cases through PubMed and Google Scholar, using the terms “HIV,” “AIDS,” “ritonavir,” “didanosine,” “maculopathy,” “retinopathy,” “visual loss,” and “toxicity” to retrieve the appropriate literature on the subject.

Results: Patient 1: A 49-year-old woman complained of progressive central visual loss over the past 12 months. History disclosed ongoing ritonavir therapy for the past 11 years. Ritonavir maculopathy was diagnosed, and visual loss increased relentlessly despite cessation of treatment. Patient 2: A 55-year-old man complained of slowly progressive peripheral visual field constriction for the past 5 years. History disclosed didanosine therapy for 13 years, however, stopped 4 years before the onset of visual symptoms. No alteration of therapy was offered to patient 2 as didanosine therapy was interrupted 9 years previously. Since 2011, 11 cases of ritonavir maculopathy have been reported in the literature. Relentless worsening of vision was reported in 3/7 patients despite cessation of ritonavir therapy. Didonasine peripheral retinopathy was first described in 1992, and a total of 24 patients have been reported since. Relentlessly progressive peripheral retinopathy was diagnosed despite the previous cessation of therapy in 14 patients.

Conclusion: Ritonavir causes a slowly progressive atrophic maculopathy, and didanosine toxicity results in a relentlessly progressing peripheral atrophic retinopathy. The relentless progression of both toxic retinopathies reflects permanent alterations of the retinal metabolism by these medications. Both ritonavir and didanosine toxic retinopathies are rare events, but their clinical presentation is highly specific.

PANRETINAL RITONAVIR-INDUCED RETINOPATHY: A REPORT OF LONG-TERM USE

PURPOSE

To report a case involving a patient with presumed panretinal ritonavir-induced retinopathy.

METHODS

A 52-year-old, HIV-positive patient, with no criteria for AIDS associated with the use of ritonavir for more than 10 years, underwent clinical examination, fundus photography, spectral domain optical coherence tomography, and fundus autofluorescence imaging.

RESULTS

Fundus examination revealed areas of atrophy and hypertrophy in the retinal pigment epithelium throughout the retina. Laboratory tests for other diseases were all negative.

CONCLUSION

HIV-positive patients undergoing ritonavir therapy should be carefully followed in the presence of low-acuity vision complaints and retinal changes.

Possible Retinal Impairment Secondary to Ritonavir Use in SARS-CoV-2 Patients: A Narrative Systematic Review

Some reports described a possible ritonavir-related retinal toxicity. The objective of this research was to review and analyze previous studies conducted on ritonavir administration and retinal impairment in a narrative synthesis. PubMed was used to perform a systematic review of ritonavir effects and retinal damage. All studies up to December 2019 were considered. Seven single cases and one case series, reporting a total of 10 patients affected by retinal changes secondary to long-term ritonavir treatment, were included in the review. Variable degrees of outer retina and retinal pigment epithelium changes were detected in most of the patients, with two patients showing macular telangiectasia, four patients presenting intraretinal crystal deposits, two patients disclosing a bull's eye maculopathy, and two patients revealing midperipheral bone spicule-like pigment changes. In the present study, we hypothesized that the use of ritonavir in life-saving treatments of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pneumonia might expose these patients to the risk of developing a retinotoxicity. We aimed to alert ophthalmologists on the importance of recognizing ritonavir-induced retinal impairment in SARS-CoV-2 patients. These findings are the target for personalized medicine.

Ritonavir associated maculopathy- multimodal imaging and electrophysiology findings

Purpose

To report the case 47-year-old patient presenting with severe maculopathy associated with long-term ritonavir treatment.

Methods

Observational case report of one patient and literature review.

Results

A 47 year-old Caucasian man presented with progressive bilateral vision loss for the past 5 years. His medical history included Human Immunodeficiency Virus (HIV) and Hepatitis C Virus (HCV) coinfection since 1992. He was treated by highly active antiretroviral therapy for 24 years including 4 years of didanosine treatment and 18 years of ritonavir treatment. Bilateral extensive macular atrophy with foveal sparing on the left eye and absence of midperipheral/peripheral retina involvement was confirmed on multimodal imaging and functional testing including swept-source OCT angiography and electroretinography.

Conclusion

Ritonavir associated maculopathy is a scarcely described medication-associated retinopathy. In this case, an extensive macular atrophy (with complete loss of photoreceptor, RPE and choriocapillaris layers) and subsequent cone-rod dysfunction appeared after 18 years of ritonavir exposure.

The Impact of Matrix Metalloproteinase-9 on the Sequential Steps of the Metastatic Process

In industrialized countries, cancer is the second leading cause of death after cardiovascular disease. Most cancer patients die because of metastases, which consist of the self-transplantation of malignant cells in anatomical sites other than the one from where the tumor arose. Disseminated cancer cells retain the phenotypic features of the primary tumor, and display very poor differentiation indices and functional regulation. Upon arrival at the target organ, they replace preexisting, normal cells, thereby permanently compromising the patient's health; the metastasis can, in turn, metastasize. The spread of cancer cells implies the degradation of the extracellular matrix by a variety of enzymes, among which the matrix metalloproteinase (MMP)-9 is particularly effective. This article reviews the available published literature concerning the important role that MMP-9 has in the metastatic process. Additionally, information is provided on therapeutic approaches aimed at counteracting, or even preventing, the development of metastasis via the use of MMP-9 antagonists.

The Anti-Angiogenic Effects of Anti-Human Immunodeficiency Virus Drugs

The growth and metastasis of malignant tumors benefit from the formation of blood vessels within the tumor area. There, new vessels originate from angiogenesis (the sprouting of pre-existing neighboring vessels) and/or vasculogenesis (the mobilization of bone marrow-derived endothelial cell precursors which incorporate in tumor vasculature and then differentiate into mature endothelial cells). These events are induced by soluble molecules (the angiogenic factors) and modulated by endothelial cell interactions with the perivascular matrix. Given angiogenesis/vasculogenesis relevance to tumor progression, anti-angiogenic drugs are often employed to buttress surgery, chemotherapy or radiation therapy in the treatment of a wide variety of cancers. Most of the anti-angiogenic drugs have been developed to functionally impair the angiogenic vascular endothelial growth factor: however, this leaves other angiogenic factors unaffected, hence leading to drug resistance and escape. Other anti-angiogenic strategies have exploited classical inhibitors of enzymes remodeling the perivascular matrix. Disappointingly, these inhibitors have been found toxic and/or ineffective in clinical trials, even though they block angiogenesis in pre-clinical models. These findings are stimulating the identification of other anti-angiogenic compounds. In this regard, it is noteworthy that drugs utilized for a long time to counteract human immune deficiency virus (HIV) can directly and effectively hamper molecular pathways leading to blood vessel formation. In this review the mechanisms leading to angiogenesis and vasculogenesis, and their susceptibility to anti-HIV drugs will be discussed.

Case Report: Retinal Toxicity Secondary to Ritonavir

SIGNIFICANCE

Because patients with HIV have increased life expectancies with the advent of new drug therapies, complications from iatrogenic syndromes such as drug toxicity can occur. Ritonavir-induced retinal toxicity is one such complication but has rarely been reported in the literature.

PURPOSE

This case report describes a patient with bilateral maculopathy and bone spicule-like pigmentary changes in the midperipheral retina due to ritonavir use. In addition, novel optical coherence tomography findings are described.

CASE REPORT

A 53-year-old man presented with gradual-onset blurry vision and difficulty seeing at night. He had been diagnosed as having HIV infection 19 years prior and had previously taken ritonavir for 7 years as part of highly active antiretroviral therapy. Best-corrected acuities were 20/30 in the right eye and 20/25 in the left eye. Clinical examination revealed a subtle annular pattern of retinal pigment epithelium mottling around the fovea and bone spicule-like pigment changes in the midperiphery of both retinas. Optical coherence tomography imaging revealed abnormal subfoveal hyperreflectivity of the ellipsoid zone with relative attenuation centrally, annular parafoveal ellipsoid zone loss, and punctate hyperreflectivity within the ellipsoid zone more eccentrically. Fundus autofluorescence in both eyes showed annular hyperautofluorescence in the parafoveal region, geographic hyperautofluorescence in the areas underlying the midperipheral pigmentary changes, and discrete patches of hyperautofluorescence along the far inferotemporal arcades in areas that appeared normal with biomicroscopy. A diagnosis of retinal toxicity secondary to ritonavir use was made based on the patient's history and clinical examination.

CONCLUSIONS

Ritonavir retinal toxicity seems to be an uncommon adverse event that can cause decreased visual function. This case report provides further evidence of the retinal toxicity and reviews the reported clinical and optical coherence tomography manifestations of the disease.

Prodrug of epigallocatechin-3-gallate alleviates choroidal neovascularization via down-regulating HIF-1α/VEGF/VEGFR2 pathway and M1 type macrophage/microglia polarization

Age-related macular degeneration (AMD) is a leading cause of vision loss in the elderly and is attributed to choroidal neovascularization (CNV), which is a feature of wet AMD. The hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF)/VEGF receptor 2 (VEGFR2) pathway contributes to the pathogenesis of CNV. M1-type macrophages/microglia secrete interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α), facilitating the development of CNV. Epigallocatechin-3-gallate (EGCG) is a kind of polyphenol in green tea that exerts anti-inflammatory and antiangiogenic effects. In this study, a prodrug of EGCG (pro-EGCG) alleviated mouse laser-induced CNV leakage and reduced CNV area by down-regulating HIF-1α/VEGF/VEGFR2 pathway; M1-type macrophage/microglia polarization; as well as endothelial cell viability, proliferation, migration and tube formation, indicating a novel potential therapy for AMD.

Inhibition of Obtusifolin on retinal pigment epithelial cell growth under hypoxia

AIM

To explore the effect of Obtusifolin on retinal pigment epithelial cell growth under hypoxia.

METHODS

In vitro chemical hypoxia model of ARPE-19 cells was established using cobalt chloride (CoCl₂). Cell viability was tested by cell counting kit-8 (CCK-8) assay. Western blot and real-time quantitative polymerase chain reaction were applied to detect proteins and mRNAs respectively. Flow cytometry was used to examine the cell cycle. Secretion of vascular endothelial growth factor (VEGF) was tested by using enzyme linked immunosorbent assay (ELISA).

RESULTS

Under the chemical hypoxia model established by CoCl₂, hypoxia inducible factor-1α (HIF-1α) mRNA and protein levels was up-regulated. Cell viability was increased and the proportion of S phase was higher. Obtusifolin could reduce cell viability under hypoxic conditions and arrest cells in G1 phase. Obtusifolin reduced the expression of Cyclin D1 and proliferating cell nuclear antigen (PCNA) in the hypoxic environment and increased the expression of p53 and p21. The levels of VEGF, VEGFR2 and eNOS proteins and mRNA were significantly increased under hypoxia while Obtusifolin inhibited the increasing.

CONCLUSION

Obtusifolin can inhibit cell growth under hypoxic conditions and down-regulate HIF-1/VEGF/eNOS secretions in ARPE-19 cells.

Self-Assembling Topical Nanomicellar Formulation to Improve Curcumin Absorption Across Ocular Tissues

The pathophysiological mechanisms for dry and wet age-related macular degeneration (AMD) involve oxidative stress and increased VEGF release and expression. An ideal drug candidate for both types of AMD is the one which offers significant protection to the retinal cells from oxidative stress and inhibit VEGF release. Curcumin is one such natural product which provides numerous beneficial effects including antioxidant, anti-inflammatory, and anti-VEGF activities and has the potential for the treatment of both types of AMD. The bioavailability of curcumin is negligible due to its poor aqueous solubility. The purpose of this work is to develop an aqueous nanomicellar drop formulation of curcumin (CUR-NMF) for back of the eye delivery utilizing hydrogenated castor oil (HCO-40) and octoxynol-40 (OC-40) to treat AMD. A full factorial design was performed with JMP software analysis to optimize the formulation size, polydispersity index (PDI), entrapment efficiency, loading, and precipitation. MTT and LDH assays on human retinal pigmented epithelial (D407) cells revealed that 5-10 μM CUR-NMF dose is safe for ophthalmic use. Furthermore, CUR-NMF exhibited significant protection of retinal (D407) cells against H₂O₂-induced oxidative stress. In vitro drug release kinetics suggested a sustained drug release profile indicating a long-term protection ability of CUR-NMF against oxidative stress to retinal cells. In addition, an ELISA suggested that CUR-NMF significantly reduces vascular endothelial growth factor (VEGF) release in D407 cell line, hence diminishes the risk of angiogenesis. Collectively, these results suggest that the proposed CUR-NMF can be tremendously effective in treating both types of AMD.

HIF-1α-induced xenobiotic transporters promote Th17 responses in Crohn's disease

In Crohn's disease, pathogenic Th17-cells express low levels of CD39 ectonucleotidase and are refractory to the immunosuppressive effects of unconjugated bilirubin (UCB), an endogenous ligand for aryl-hydrocarbon-receptor (AhR). This resistance to AhR ligation might be associated with alterations in responses to hypoxia. Limited exposure to hypoxia appears beneficial in acute tissue injury. However, in protracted inflammation, hypoxemia may paradoxically result in Th17-cell activation. We report here that in vitro exposure of Th17-cells from Crohn's disease patients to hypoxia limits responsiveness to AhR stimulation by UCB, as reflected by lower CD39 levels. Blockade of hypoxia-inducible-factor-1alpha (HIF-1α) upregulates CD39 and favors Th17-cell regulatory responses. Resistance of Th17-cells to AhR signaling results, in part, from HIF-1α-dependent induction of ATP-binding cassette (ABC) transporters: multidrug-resistance-protein-1 (MDR1) and multidrug-resistance-associated-protein-4 (MRP4). Increased ABC transporters promote efflux of suppressive AhR ligands, such as UCB, from Th17-cells. Inhibition of MDR1, MRP4 and/or HIF-1α with ritonavir (RTV) reconstitutes AhR function in Th17-cells, enhancing therapeutic effects of UCB in dextran-sulfate-sodium-induced experimental colitis. Deleterious effects of hypoxia on Th17-cells in Crohn's disease can be ameliorated either by inhibiting HIF-1α or by suppressing ABC transporters to increase UCB availability as an AhR substrate. Targeting HIF-1α-ABC transporters could provide innovative therapeutic pathways for IBD.

Plasma levels of hypoxia-regulated factors in patients with age-related macular degeneration

PURPOSE

Various hypoxia-related proteins are differentially expressed in the retina and secreted to the vitreous and/or aqueous humor of patients affected by dry or neovascular age-related macular degeneration (nAMD). To determine whether these conditions alter concentrations of cytokines also in the systemic circulation, we measured plasma levels of six hypoxia-related proteins.

METHODS

Plasma was prepared from EDTA blood that was collected from patients affected by dry AMD (n = 5), nAMD (n = 11), proliferative diabetic retinopathy (PDR; n = 9), and patients with an epiretinal membrane (ERM; n = 11). ERM samples served as negative controls, PDR samples as positive controls. Protein concentrations of vascular endothelial growth factor (VEGF), erythropoietin (EPO), angiopoietin-like 4 (ANGPTL4), placental growth factor (PlGF), tumor necrosis factor alpha (TNF-α), and pigment epithelium-derived factor (PEDF) were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The concentration of PlGF was significantly increased in plasma of patients affected by nAMD. Although no statistically significant differences were found for EPO, ANGPTL4, PlGF, TNF-α, and PEDF, the mean concentration of VEGF was lowest in the nAMD group. Plasma concentrations of the six factors did not correlate with gender or age of patients.

CONCLUSIONS

nAMD may increase plasma concentrations of PlGF, making it a candidate as a biomarker for the neovascular form of AMD. Other factors, however, were not differentially regulated, suggesting that their systemic concentrations are not generally increased in hypoxia-related retinal diseases.

Tanshinone IIA Inhibits VEGF Secretion and HIF-1α Expression in Cultured Human Retinal Pigment Epithelial Cells under Hypoxia

PURPOSE

The current work intends to study the activity of tanshinone IIA on secretion of vascular endothelial growth factor (VEGF) and expression of hypoxia inducible factor 1α (HIF-1α) in human retinal pigment epithelial cells (ARPE-19 cells) under hypoxic condition.

METHODS

The cytotoxicity of tanshinone IIA was tested in ARPE-19 cells by MTT assay. ARPE-19 cells were incubated with different concentrations of cobalt chloride (100, 150, and 200 µM) for 12 h, and levels of expressed HIF-1α and secreted VEGF were quantified through Western blot and ELISA, respectively. Further, ARPE-19 cells were pretreated for 1 h with different concentrations of tanshinone IIA (5, 10, 15, and 18 µM). After 1 h, the cells were subjected to hypoxic condition using 150 µM cobalt chloride for 12 h in the presence and absence of tanshinone IIA. The cells were then harvested, and the secreted VEGF and expressed HIF-1α was studied.

RESULTS

Tanshinone IIA at concentrations of 5, 10, 15, and 18 μM did not show cytotoxicity in ARPE-19 cells. Chemical hypoxia induced by cobalt chloride caused a significant increase in VEGF level in a dose-dependent manner, and HIF-1α expression peaked at 150 µM. Based on the data, cobalt chloride concentration was maintained at 150 μM for further studies. Tanshinone IIA decreased the level of HIF-1α and VEGF secretion in a dose-dependent manner under hypoxic condition.

CONCLUSION

Tanshinone IIA could be explored as a new potential candidate for treating wet AMD.

Electrophysiological features and multimodal imaging in ritonavir-related maculopathy

PURPOSE

The purpose of this study is to report a case of ritonavir-related retinal toxicity followed over a year. Electrophysiological features and multimodal imaging, including adaptive optics, are provided and discussed.

METHODS

Electrophysiological recordings and multimodal imaging were performed and repeated over 1 year.

RESULTS

Fundus examination revealed crystalline maculopathy in conjunction with pigment disruption. Spectral domain optical coherence tomography displayed thinning of the macula without cysts. Autofluorescence imaging revealed a mixed pattern of complete loss of the autofluorescence in the area of retinal pigment deposit and an increased transmission of the autofluorescence in the area of retinal thinning. Fluorescein angiography ruled out parafoveal telangiectasia. Indocyanine green angiography was not contributive. Increased spacing of the macular cone mosaic, crystal deposits and pigment migrations were seen with adaptive optics. Full-field electroretinogram was slightly reduced for both eyes, especially in the light-adapted responses, and mfERG confirmed bilateral maculopathy. Functional and structural abnormalities did not change with follow-up besides constant pigmentary changes monitored with adaptive optics.

CONCLUSION

Ritonavir-related retinal toxicity is a maculopathy with peculiar features including crystalline and pigment migration associated with central or temporofoveolar thinning and inconstant macular telangiectasia. Despite drug cessation, retinal remodelling continues to progress.

Prominin-1 Is a Novel Regulator of Autophagy in the Human Retinal Pigment Epithelium

Purpose

Prominin-1 (Prom1) is a transmembrane glycoprotein, which is expressed in stem cell lineages, and has recently been implicated in cancer stem cell survival. Mutations in the Prom1 gene have been shown to disrupt photoreceptor disk morphogenesis and cause an autosomal dominant form of Stargardt-like macular dystrophy (STGD4). Despite the apparent structural role of Prom1 in photoreceptors, its role in other cells of the retina is unknown. The purpose of this study is to investigate the role of Prom1 in the highly metabolically active cells of the retinal pigment epithelium (RPE).

Methods

Lentiviral siRNA and the genome editing CRISPR/Cas9 system were used to knockout Prom1 in primary RPE and ARPE-19 cells, respectively. Western blotting, confocal microscopy, and flow sight imaging cytometry assays were used to quantify autophagy flux. Immunoprecipitation was used to detect Prom1 interacting proteins.

Results

Our studies demonstrate that Prom1 is primarily a cytosolic protein in the RPE. Stress signals and physiological aging robustly increase autophagy with concomitant upregulation of Prom1 expression. Knockout of Prom1 increased mTORC1 and mTORC2 signaling, decreased autophagosome trafficking to the lysosome, increased p62 accumulation, and inhibited autophagic puncta induced by activators of autophagy. Conversely, ectopic overexpression of Prom1 inhibited mTORC1 and mTORC2 activities, and potentiated autophagy flux. Through interactions with p62 and HDAC6, Prom1 regulates autophagosome maturation and trafficking, suggesting a new cytoplasmic role of Prom1 in RPE function.

Conclusions

Our results demonstrate that Prom1 plays a key role in the regulation of autophagy via upstream suppression of mTOR signaling and also acting as a component of a macromolecular scaffold involving p62 and HDAC6.

Bull's eye maculopathy in an HIV-positive patient receiving ritonavir

Retinal toxicity involving the macula as a complication of the antiretroviral protease inhibitor ritonavir has been described in a few cases. We report retinal pigment epitheliopathy involving the macula with a bull's eye pattern in a 36-year-old man with well-controlled HIV receiving ritonavir with gradually progressive bilateral vision loss.

Delivery strategies for treatment of age-related ocular diseases: From a biological understanding to biomaterial solutions

Age-related ocular diseases, such as age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma, result in life-long functional deficits and enormous global health care costs. As the worldwide population ages, vision loss has become a major concern for both economic and human health reasons. Due to recent research into biomaterials and nanotechnology major advances have been gained in the field of ocular delivery. This review provides a summary and discussion of the most recent strategies employed for the delivery of both drugs and cells to the eye to treat a variety of age-related diseases. It emphasizes the current challenges and limitations to ocular delivery and how the use of innovative materials can overcome these issues and ultimately provide treatment for age-related degeneration and regeneration of lost tissues. This review also provides critical considerations and an outlook for future studies in the field of ophthalmic delivery.

Dickkopf‑related protein 1 induces angiogenesis by upregulating vascular endothelial growth factor in the synovial fibroblasts of patients with temporomandibular joint disorders

Angiogenesis has an important role in the progression of temporomandibular joint disorders (TMD). The aim of the present study was to explore the association between dickkopf-related protein 1 (DKK-1) and angiogenesis in TMD. The expression levels of DKK-1 and vascular endothelial growth factor (VEGF) were quantified by an ELISA assay of the synovial fluid from patients with TMD. The correlation between DKK-1 and VEGF was analyzed by Pearson correlation test. Synovial fibroblasts were isolated from patients with TMD and were subsequently treated with recombinant human DKK-1, anti-DKK-1 antibody, hypoxia inducible factor-1α (HIF-1α), or small interfering RNA (siRNA). The expression levels of DKK-1, HIF-1α, and VEGF were subsequently quantified. The present study also investigated the effects of DKK-1 on the migration of human umbilical vein endothelial cells (HUVEC). Increased expression levels of DKK-1 were concordant with increased expression levels of VEGF in the synovial fluid from patients with TMD. In the synovial fibroblasts, DKK-1 increased the expression levels of VEGF, and promoted HIF-1α nuclear localization. In addition, DKK-1 induced HUVEC migration, and HIF-1α siRNA inhibited DKK-1-induced cell migration. The results of the present study indicate that DKK-1 is associated with angiogenesis in the synovial fluid of patients with TMD. Furthermore, HIF-1α may be associated with DKK-1-induced HUVEC activation.

3,3'-Diindolylmethane inhibits VEGF expression through the HIF-1α and NF-κB pathways in human retinal pigment epithelial cells under chemical hypoxic conditions

Oxidative stress in the retinal pigment epithelium (RPE) can lead to the pathological causes of age-related macular degeneration (AMD). Hypoxia induces oxidative damage in retinal pigment epithelial cells (RPE cells). In this study, we investigated the capacity of 3,3'-diindolylmethane (DIM) to reduce the expression of vascular endothelial growth factor (VEGF) under hypoxic conditions, as well as the molecular mechanisms involved. Human RPE cells (ARPE-19 cells) were treated with cobalt chloride (CoCl2, 200 µM) and/or DIM (10 and 20 µM). The production of VEGF was measured by enzyme-linked immunosorbent assay. The translocation of hypoxia-inducible factor-1α (HIF-1α) and nuclear factor-κB (NF-κB) was determined by western blot analysis. The binding activity of HIF-1α and NF-κB was analyzed by electrophoretic mobility shift assay. The phosphorylation levels of mitogen-activated protein kinases (MAPKs) were measured by western blot analysis. The levels of mitochondrial reactive oxygen species (ROS) were detected by fluorescence microplate assay. The results revealed that DIM significantly attenuated the CoCl2-induced expression of VEGF in the ARPE-19 cells. The CoCl2-induced translocation and activation of HIF-1α and NF-κB were also attenuated by treatment with DIM. In addition, DIM inhibited the CoCl2-induced activation of p38 MAPK in the ARPE-19 cells. Pre-treatment with YCG063, a mitochondrial ROS inhibitor, led to the downregulation of the CoCl2-induced production of VEGF by suppressing HIF-1α and NF-κB activity. Taken together, the findings of our study demonstrate that DIM inhibits the CoCl2-induced production of VEGF by suppressing mitochondrial ROS production, thus attenuating the activation of HIF-1α and p38 MAPK/NF-κB.

Caffeic acid phenethyl ester reduces the secretion of vascular endothelial growth factor through the inhibition of the ROS, PI3K and HIF-1α signaling pathways in human retinal pigment epithelial cells under hypoxic conditions

Choroidal neovascularization (CNV) can lead to progressive and severe visual loss. Vascular endothelial growth factor (VEGF) promotes the development of CNV. Caffeic acid phenethyl ester (CAPE), a biologically active component of the honeybee (Apis mellifera) propolis, has been demonstrated to have several interesting biological regulatory properties. The objective of this study was to determine whether treatment with CAPE results in the inhibition of the production of vascular endothelial growth factor (VEGF) in retinal pigment epithelial cells (RPE cells) under hypoxic conditions and to explore the possible underlying mechanisms. An in vitro experimental model of hypoxia was used to mimic an ischemic microenvironment for the RPE cells. Human RPE cells (ARPE-19) were exposed to hypoxia with or without CAPE pre-treatment. ARPE-19 cells were used to investigate the pathway involved in the regulation of VEGF production under hypoxic conditions, based on western blot analysis, enzyme-linked immunosorbent assay (ELISA) and electrophoretic mobility shift assay (EMSA). The amount of VEGF released from the hypoxia-exposed cells was significantly higher than that of the normoxic controls. Pre-treatment with CAPE suppressed the hypoxia-induced production of VEGF in the ARPE-19 cells, and this effect was inhibited through the attenuation of reactive oxygen species (ROS) production, and the inhibition of phosphoinositide 3-kinase (PI3K)/AKT and hypoxia-inducible factor-1α (HIF-1α) expression. These in vitro findings suggest that CAPE may prove to be a novel anti-angiogenic agent for the treatment of diseases associated with CNV.

Involvement of RhoA/ROCK1 signaling pathway in hyperglycemia-induced microvascular endothelial dysfunction in diabetic retinopathy

Diabetic retinopathy (DR) is a well-known serious complication of diabetes mellitus (DM), and can eventually advance to end-stage blindness. In the early stage of DR, endothelial cell barrier disorganized primarily and tight junction (TJ) protein composition transformed subsequently. The small GTPase RhoA and its downstream effector Rho-associated coiled-coil containing protein kinase 1 (ROCK1) regulate a mass of cellular processes, including cell adherence, proliferation, permeability and apoptosis. Although RhoA inhibitors have provided substantial clinical benefit as hypertonicity therapeutics, their use is limited by complex microenvironment as DR. While ample evidence indicates that TJ can be influenced by the RhoA/ROCK1 signaling, the underlying mechanisms remain incompletely understood. Here, we have uncovered a significant signaling network involved in diabetic retinal microvascular endothelial dysfunction (RMVED). Our results indicated that the activation of RhoA/ROCK1 pathway due to high glucose played a key role in microvascular endothelial cell dysfunction (MVED) by way of directly inducing TJ proteins over-expression during DR. We demonstrated that inhibition of RhoA/ROCK1 may attenuate the hypertonicity of endothelial cell caused by high glucose microenvironment meanwhile. Besides, chemical and pharmacological inhibitors of RhoA/ROCK1 pathway may partly block inflammation due to DR. Simultaneously, the apoptosis aroused by high glucose was also prevented considerably by fasudil, a kind of pharmacological inhibitor of RhoA/ROCK1 pathway. These findings indicate that RhoA/ROCK1 signaling directly modulates MVED, suggesting a novel therapeutic target for DR.